From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423666AbWJaVwV (ORCPT ); Tue, 31 Oct 2006 16:52:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423670AbWJaVwV (ORCPT ); Tue, 31 Oct 2006 16:52:21 -0500 Received: from nf-out-0910.google.com ([64.233.182.185]:14610 "EHLO nf-out-0910.google.com") by vger.kernel.org with ESMTP id S1423666AbWJaVwV (ORCPT ); Tue, 31 Oct 2006 16:52:21 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:from:to:subject:date:user-agent:cc:mime-version:content-type:content-transfer-encoding:content-disposition:message-id; b=B8paefeQjP6cnOr4tIgamYvK/c/qkpLmzNRk5ahXMYx3hwTfDchu8/bnAaU2T5oOb+oRoCB6jlMINXuj6FSM86bMuXhPhnC4CiQOLlpf6ONhdBLObe3ZrBfu7XbTTWbAxv3uStlQHl3mucmfgY4f0R8EhAueDfgjZCPgmAEzlMs= From: Jesper Juhl To: linux-kernel@vger.kernel.org Subject: [PATCH][RFC] potential NULL pointer deref in XFS on failed mount Date: Tue, 31 Oct 2006 22:54:00 +0100 User-Agent: KMail/1.9.4 Cc: xfs@oss.sgi.com, xfs-masters@oss.sgi.com, nathans@sgi.com, Jesper Juhl MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200610312254.00320.jesper.juhl@gmail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org The Coverity checker spotted a potential problem in XFS. The problem is that if, in xfs_mount(), this code triggers: ... if (!mp->m_logdev_targp) goto error0; ... Then we'll end up calling xfs_unmountfs_close() with a NULL 'mp->m_logdev_targp'. This in turn will result in a call to xfs_free_buftarg() with its 'btp' argument == NULL. xfs_free_buftarg() dereferences 'btp' leading to a NULL pointer dereference and crash. I think this can happen, since the fatal call to xfs_free_buftarg() happens when 'm_logdev_targp != m_ddev_targp' and due to a check of 'm_ddev_targp' against NULL in xfs_mount() (and subsequent return if it is NULL) the two will never both be NULL when we hit the error0 label from the two lines cited above. Comments welcome (please keep me on Cc: on replies). Here's a proposed patch to fix this by testing 'btp' against NULL in xfs_free_buftarg(). Signed-off-by: Jesper Juhl --- fs/xfs/linux-2.6/xfs_buf.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c index db5f5a3..6ef1860 100644 --- a/fs/xfs/linux-2.6/xfs_buf.c +++ b/fs/xfs/linux-2.6/xfs_buf.c @@ -1450,6 +1450,9 @@ xfs_free_buftarg( xfs_buftarg_t *btp, int external) { + if (unlikely(!btp)) + return; + xfs_flush_buftarg(btp, 1); if (external) xfs_blkdev_put(btp->bt_bdev);